There have been known plunger pumps in which a drive member such as an eccentric cam reciprocates a plunger (also called a piston) within a pump chamber in the axial direction to cause a fluid sucked into the pump chamber through a suction port to be discharged through a discharge port of the pump chamber.
Among examples of the above plunger pumps are ones that include: a pump body having a cylinder hole; a spherical lid member inserted by pressing in the cylinder hole; a plunger that defines, together with the lid member, a pump chamber and is in contact with a drive member; a seal member that is fit over the plunger; and a coiled spring that is in contact with the lid member and also with the plunger (see Patent Document 1, for example).